Ground Shaking Research Articles

Numerical modeling of a potential landslide-generated tsunami in the southern Strait of Georgia

We report results of numerical simulations of a potential subaerial landslide on the coast of Orcas Island and the resultant tsunami waves in the southern Strait of Georgia near the US/Canada border. A likely trigger is strong ground shaking during large earthquakes on the nearby Holocene active Skipjack Island fault zone. For a worst-case scenario, we assume a 0.17 {textrm{km}}^3 rigid subaerial failure on the steep northeast coast of the island, spanning the sim 5 km between previous landslide deposits on the adjacent seafloor. The landslide motion and resulting tsunami generation are modeled using the three-dimensional (3D) non-hydrostatics physics-based NHWAVE model. The simulated failure moves downslope with a peak velocity of 13.64ṁ/s and travels 732 m before coming to rest after 85 s in 75-m water depth. Tsunami propagation is then continued using the 2D fully nonlinear and dispersive Boussinesq wave model FUNWAVE-TVD in a succession of layered and nested grids. The modeling reveals susceptible locations, particularly as waves will arrive with little or no warning. In the near-source region, modeled waves have peak amplitudes of 15–20 m, current speeds of up to 10 m/s, and runup of up to 30 m. Smaller, but significant, wave amplitudes and runup occur throughout the region surrounding Orcas Island. In the tsunami propagation direction, runup reaches 7.5 m at Neptune Beach near Lummi Bay. Both initial and reflected waves cause significant runup (> 1.5 m) along much of the shoreline between Point Roberts and Lummi Bay.

Macromechanism Approach for Vulnerability Assessment of Buildings on Shallow Foundations in Liquefied Soils

The damage caused by seismic shaking and liquefaction-induced permanent ground deformation has conventionally been assessed as two separate problems often by different engineers. However, the two problems are inherently linked, since ground shaking causes liquefaction, and liquefaction-induced soil softening affects ground shaking. Modelling both problems within a single numerical model is complex for both the engineer and the software, and most finite element software only have the capabilities to address one of them. To improve the estimates of the seismic performance of buildings on liquefiable soil, a new sub-structuring approach is proposed called the macro-mechanism approach. This approach allows the soil-liquefaction-foundation-structure interaction to be considered in a series of sub-models accounting for the major nonlinear mechanisms of the system at a macro level. The proposed approach was implemented in the open-source finite element software OpenSees and then applied to a case study of a building where significant liquefaction- and shaking-induced damage was observed after the 1999 Mw 7.4 Kocaeli Earthquake. The case study building was also simulated using two different commercial software programs, the finite difference software FLAC, and the finite element software PLAXIS, by two different research teams. A comparison between the results from the macro-mechanism approach compared to full numerical models shows that the macro-mechanism approach can capture the extent of the foundation deformation and provide more realistic estimates of the building damage than full approaches since the FLAC and PLAXIS models consider elastic elements for the building.

Estimate of Responses of Multistoried Building under Earthquake Ground Motion to Prevent Failure

Seismic microzonation is defined as the process of subdividing a potential seismic or earthquake-prone area into zones with respect to some geological and geophysical characteristics of the sites such as ground shaking, liquefaction susceptibility, landslide, and rock fall hazard, earthquake-related flooding, etc. Very often, the seismic data are used from existing ground motion data that are related to other geographical regions and thus leads to unrealistic predictions. In this analysis, normalization of the available earthquake data is carried out for a better realistic prediction of building response. An extensive study is carried out in this work that involves two major types of buildings, microzones, and soil conditions. Fixed base, hard, medium, and soft soil have been considered for this analysis. The effect of actual and normalized ground motion for specific microzones having plan asymmetric and symmetric structures is not yet studied in prior research. The analysis has been done by finite element-based software. The present study makes an effort to determine the fundamental responses of plan asymmetric building in different kinds of soil in certain microzones. Maximum shear forces and bending moment have been seen in hard soil base conditions among all other supports. Responses of microzone II and actual ground motion are almost the same in dynamic analysis.

Predicting timescales of relaxation in the shallow Earth’s subsurface

Earthquakes introduce long-lasting transient mechanical damage in the subsurface, which cause postseismic hazards such as enhanced landsliding and can take years to recover to steady-state values. This observation has been linked to relaxation, a phenomenon observed in a wide class of materials after straining perturbations. In this presentation, I analyze the successive effect of two large earthquakes on ground properties through the monitoring of seismic velocity from ambient noise interferometry in the Atacama desert in Chile. The absence of rainfall in this area allows study of the mechanical state of the subsurface by limiting the potential effect of variable groundwater content. I show that relaxation timescales are a function of the current state of the subsurface when perturbed by earthquakes, rather than ground shaking intensity. Our study highlights the predictability of earthquake damage dynamics in the Earth's near-surface and potentially other materials. I propose to reconcile this paradigm with existing physical frameworks by considering the superposition of different populations of damaged contacts.

Assessment of Torsional Amplification of Drift Demand in a Building Employing Site-Specific Response Spectra and Accelerograms

This paper aims at giving structural designers guidance on how to transform seismic demand on a building structure from two-dimensional (2D) to three-dimensional (3D) in an expedient manner, taking into account amplification of the torsional actions. This paper is to be read in conjunction with either paper #3 or #4. Torsional amplification of the drift demand in a building is of major concern in the structural design for countering seismic actions on the building. Code-based seismic design procedures based on elastic analyses may understate torsional actions in a plan of asymmetric building. This is because the inability of elastic analyses to capture the abrupt increase in the torsional action as the limit of yield of the supporting structural walls is surpassed. Nonlinear dynamic analysis can provide accurate assessment of torsional actions in a building which has been excited to respond in the inelastic range. However, a 3D whole building analysis of a multi-storey building can be costly and challenging, and hence not suited to day-to-day structural design. To simplify the analysis and reduce the scale of the computation, closed-form expressions are introduced in this paper for estimation of the Δ3D/Δ2D drift demand ratio for elastic conditions when buildings are subjected to moderate-intensity ground shaking. The drift demand of the 3D model can be estimated as a product of the 2D drift demand and the Δ3D/Δ2D drift demand ratio. In dealing with higher-intensity ground shaking causing yielding to occur, a macroscopic modelling methodology may be employed. The estimated Δ3D/Δ2D drift demand ratio of an equivalent single-storey building is combined with separate analysis for determination of the 2D drift demand. The deflection profile of the multi-storey prototype taking into account 3D effects, including torsional actions, is hence obtained. The accuracy of the presented methodologies has been verified by case studies in which drift estimates generated by the proposed calculation procedure were compared against results from whole building analyses, employing a well-established computer software.

How large peak ground acceleration by large earthquakes could generate turbidity currents along the slope of northern Japan Trench

Deep-sea turbidite has been used to determine the history of occurrence of large earthquakes. Surface-sediment remobilization is a mechanism of the generation of earthquake-induced turbidity currents. However, the detailed mechanism of surface-sediment remobilization caused by earthquake ground shaking is unclear. To understand how high peak ground acceleration (PGA) caused by a large earthquake can remobilize surface sediments, we determined the age of a surface-sediment core recovered from the mid-slope terrace (MST) of the inner slope of the Japan Trench in northern Sanriku to determine turbidites generated by large historical earthquakes and calculate the PGAs of these earthquakes using an empirical attenuation relation commonly used in Japan. Small offsets in radiocarbon ages and excess 210Pb activities between turbidite and hemipelagic muds suggest that the turbidites in the core resulted from surface-sediment remobilization. 137Cs and excess 210Pb chronologies indicate that the three uppermost turbidites in the core are correlated with three large historical earthquakes, namely the 1968 common era (CE) Tokachi-oki, the 1933 CE Showa–Sanriku, and the 1896 CE Meiji–Sanriku earthquakes. Calculation of PGAs for large historical earthquakes along the northern Japan Trench indicates that a PGA of > 0.6 g is necessary for turbidite deposition in the MST basin. This threshold is larger than that reported for central Sanriku and may vary spatially. Moreover, turbidites in the MST deposits are more frequent in the northern Japan Trench than in the central Japan Trench, suggesting that the occurrence of three types of large M8-class earthquakes in the northern Japan Trench might have contributed to the frequent occurrence of large PGAs.

Numerical study on response characteristics of a caisson-type quay wall subjected to bidirectional ground shaking

The aim of this paper is to use numerical simulations to elucidate the effect of liquid–quay wall interaction on the seismic behavior of caisson-type quay wall subjected to real ground motions, assuming irrotational and inviscid flows. Three-dimensional, time-domain, dynamic analysis of a typical caisson-type quay wall is carried out using a coupled Lagrangian-Eulerian scheme, and six real excitation records are applied as ground vibration. The geometric complexity in the bounded caisson–seawater–backfill/foundation system is handled in the finite element method (FEM) using deformable 3D mesh where each structural medium can be discretized independently. The performance of the present coupled numerical analysis approach is validated against available numerical predictions, exhibiting good agreement with benchmark data. The response is appraised in terms of excess pore water pressure generated in the porous media, soil–sea–structure's residual displacements, and induced hydrodynamic pressures during the earthquake excitation. The numerical procedure demonstrates that excitation frequency spectrum in different intensity altitudes plays a crucial role in the behavior of quay walls and special attention must be given to gain a better understanding on the dynamic responses of such coupled systems.

Assessing the potential implementation of earthquake early warning for schools in the Patras region, Greece

Earthquake early warning (EEW) is currently deemed a credible approach to seismic resilience enhancement in modern societies, especially if part of a more holistic earthquake mitigation strategy involving other risk reduction tools such as structural upgrading/retrofit. Yet, there remains a strong need to 1) assess the feasibility of EEW in various seismotectonic contexts, considering specific target applications/end users; and 2) develop next-generation decision-support systems relying on interpretable probabilistic impact-based estimates toward more risk-informed decision-making on EEW installation/alert triggering. These challenges are addressed in this paper, which showcases a series of recent significant EEW contributions by the authors. First, we present the results of a state-of-the-art feasibility study for EEW in schools performed across the Patras region of Greece, attempting to spatially combine traditional seismologically-driven EEW decision criteria (i.e., warning time) with proxy risk-oriented measures for earthquake impact (i.e., building fragility and the number of exposed school students). These results show that, under certain conditions, EEW could be effective for the schools in the considered case-study region. We then demonstrate an advanced end-user-centred approach for improved risk-informed decision-making on triggering EEW alerts. The proposed methodology integrates earthquake-engineering-related seismic performance assessment procedures and metrics with multi-criteria decision-making (MCDM) within an end-to-end probabilistic framework. The performance-based earthquake engineering component of such a framework facilitates the computation of various damage/loss estimates (e.g., repair cost, downtime, and casualties) by combining target-structure-specific models of seismic response, fragility, and vulnerability with real-time ground-shaking estimates. Additionally, the incorporated MCDM methodology enables explicit consideration of end-user preferences (importance) towards the estimated consequences in the context of alert issuance. The developed approach is demonstrated using an archetype school building for the case-study region, for which we specifically investigate the optimal decision (i.e., “trigger” or “don't trigger” an EEW alert) across a range of ground-motion intensity measures. We find that the best action for a given level of ground shaking can vary as a function of stakeholder preferences.

A framework to quantify the effectiveness of earthquake early warning in mitigating seismic risk

Earthquake early warning systems (EEWSs) aim to rapidly detect earthquakes and provide timely alerts, so that users can take protective actions prior to the onset of strong ground shaking. The promise and limitations of EEWSs have both been widely debated. On one hand, an operational EEWS could mitigate earthquake damage by triggering potentially cost- and life-saving actions. These range from automated system responses such as slowing down trains to the actions of individuals that receive the alerts and take protective measures. On the other hand, the effectiveness of an EEWS is conditional on the ability to issue warnings that are sufficiently accurate and timely to facilitate an appropriate action. The refinement of earthquake early warning (EEW) algorithms and the installation of denser and faster seismic networks have improved performance; however, the benefit in risk reduction that an EEWS could achieve remains unquantified. In this study, we leverage upon regional event-based probabilistic seismic risk assessment to devise a quantitative and fully customizable framework for evaluating the effectiveness of EEW in mitigating seismic risk. We demonstrate this framework using Switzerland as a testbed, for which we compute and contrast human loss exceedance curves with and without EEW.

The Importance of Assessing the Geological Site Effects of Ancient Earthquakes from the Archaeoseismological Point of View

Earthquakes have and continue to, occur worldwide, though some places are affected more than others by earthquake-induced ground shaking and the same earthquake can cause more damage in one area than in nearby locations due to site-specific geological site conditions, also known as local site effects. Depending on the chronology of the earthquakes, various disciplines of seismology include instrumental and historical seismology, archaeoseismology, palaeoseismology and neotectonics, each focusing on using specific sources of information to evaluate recent or ancient earthquakes. Past earthquakes are investigated to expand the pre-instrumental and instrumental earthquake catalog and better evaluate a region’s seismic hazard. Archaeoseismology offers a way to achieve these goals because it links how ancient civilizations and their environment might have interacted and responded to past earthquake-induced ground motion and soil amplification. Hence, archaeoseismology explores pre-instrumental (past) earthquakes that might have affected sites of human occupation and their nearby settings, which have left their co-seismic marks in ancient manufactured constructions exhumed by archaeological excavations. However, archaeoseismological observations are often made on a limited epicentral area, poorly constrained dated earthquakes and occasionally on unclear evidence of earthquake damage. Archaeological excavations or field investigations often underestimate the critical role that an archaeological site’s ancient geological site conditions might have played in causing co-seismic structural damage to ancient anthropogenic structures. Nevertheless, the archaeological community might document and inaccurately diagnose structural damage by ancient earthquake shaking to structures and even estimate the size of past earthquakes giving little or no consideration to the role of geological site effects in addressing the causative earthquake. This mixture of factors frequently leads to imprecise estimates of the size of ancient earthquakes and unlikely earthquake environmental impacts, leaving unexplained the location and the moment magnitude of the causative earthquake. Hence, it is essential not to rely solely on earthquake intensities based on archaeologically documented co-seismic damage without assessing the nature of the observed structural damage and the contribution of the geological site effects. This paper explains the geological site effects concept to archaeologists unfamiliar with the notion. It clarifies its role in assessing ground shaking, soil amplification and earthquake intensity by past earthquakes and how and why the geological site effects can be estimated when a site is thought to have been struck by an earthquake. Hence, the geological site effects must be considered when archaeological excavations describe and interpret destruction layers. Conversely, engineers and seismologists dealing with seismic hazard risk assessment must pay close attention to archaeological investigations assessing earthquake intensities and locations based on field evidence of damage to structures attributed to past earthquakes, because the geological site effects might have been factored in inaccurately or not at all.

Mapping of Soil Liquefaction Associated with the 2021 Mw 7.4 Maduo (Madoi) Earthquake Based on the UAV Photogrammetry Technology

The 2021 Mw 7.4 Maduo (Madoi) earthquake that struck the northern Tibetan Plateau resulted in widespread coseismic deformation features, such as surface ruptures and soil liquefaction. By utilizing the unmanned aerial vehicle (UAV) photogrammetry technology, we accurately recognize and map 39,286 liquefaction sites within a 1.5 km wide zone along the coseismic surface rupture. We then systematically analyze the coseismic liquefaction distribution characteristics and the possible influencing factors. The coseismic liquefaction density remains on a higher level within 250 m from the surface rupture and decreases in a power law with the increasing distance. The amplification of the seismic waves in the vicinity of the rupture zone enhances the liquefaction effects near it. More than 90% of coseismic liquefaction occurs in the peak ground acceleration (PGA) > 0.50 g, and the liquefaction density is significantly higher in the region with seismic intensity > VIII. Combined with the sedimentary distribution along-strike of the surface rupture, the mapped liquefaction sites indicate that the differences in the sedimentary environments could cause more intense liquefaction on the western side of the epicenter, where loose Quaternary deposits are widely spread. The stronger coseismic liquefaction sites correspond to the Eling Lake section, the Yellow River floodplain, and the Heihe River floodplain, where the soil is mostly saturated with loose fine-grained sand and the groundwater level is high. Our results show that the massive liquefaction caused by the strong ground shaking during the Maduo (Madoi) earthquake was distributed as the specific local sedimentary environment and the groundwater level changed.

A review of pre-disaster public awareness activities on public readiness: The 2010 Mentawai tsunami

A qualitative study on impact of pre-disaster public awareness activities on public readiness was conducted in the North and South Pagai Islands after the 25 October 2010 Mentawai earthquake. Parameters of readiness are public response to tsunami and the number of casualties. The results show that public awareness activities that commenced from 2004 have effectively increased people's awareness of tsunamis as indicated by their knowledge of tsunami signals. Yet apart from failure of the official warning system to alert the public in remote areas, the response of people to the natural tsunami signals has been made on the basis of misperceptions of strong earthquake signals and tsunami lead-time. Tsunami lead-time of the Pagai Islands had been perceived as long as that of Sumatra or Java Islands and strong earthquakes have been perceived as merely strong ground shaking. These misperceptions came from invalid materials of public education and invalid translation of scientific information, and were confirmed by people's experiences in the 12 September 2007 Bengkulu earthquake. Hence, despite mitigation by relocating houses to the high ground that has saved many lives in Malakopa and Asahan, there is no evidence on the positive relation of pre-disaster awareness intervention with the reduction in loss of lives in the study sites. In order to not give invalid information on tsunami awareness in the future, instead of using a generic formula of regional tsunamis, public education on tsunami should use a specific formula based on local characteristics. Moreover, sensing earthquakes that may trigger tsunamis through the duration of ground shaking may be more effective than that of the strength of ground shaking. Because sensing time duration is difficult, particularly for communities that are not used to using modern timers, it is necessary to develop simple means of sensing time duration.

A simplified three-dimensional constitutive model for seismic modeling of dense sands

Dense sands subjected to earthquake shaking may not liquefy but experience differential settlements that can cause damage or limit the serviceability of overlying structures and utilities. Such settlements can be estimated using stress and/or strain based empirical models in conjunction with one-dimensional site response analyses utilizing normalized modulus reduction and damping curves and uni-directional ground shaking. Multi-directional effects are incorporated through applying additional factors. In contrast, there are limited number of studies on the three-dimensional (3-D) modeling of shear induced seismic response of sands. In this study, a simplified, mean stress-dependent constitutive model (termed I-soil) is presented for dense sands. The model adopts the framework of a class of multi-dimensional distributed-element models for cyclic plasticity applications. I-soil extends this framework for soil applications by adding non-Masing un/reloading rules and simplified shear induced volumetric response formulation. The shear response parameters can be calibrated using shear wave velocity, widely used normalized modulus reduction and damping curves. The shear induced volumetric response is calibrated using cyclic direct simple shear tests. Default values for model parameters and dynamic curves are proposed. The resulting model was implemented in a dynamic finite-element analysis platform, LS-DYNA. It is shown that simulations can capture the seismic shear and volumetric behavior of saturated sands measured under partially drained conditions in dynamic centrifuge tests.

Resolving minute temporal seismic velocity changes induced by earthquake damage: the more stations, the merrier?

SUMMARYGround shaking induced by earthquakes often introduces transient changes in seismic velocity monitored with ambient noise. These changes are usually attributed to relaxation behaviour following the coseismic damage in the subsurface and are of relevance for post-seismic hazard mitigation. However, the velocity evolution associated with this phenomenon can occur at very small timescales and amplitudes that are not resolved with seismic interferometry and are therefore challenging to link to laboratory experiments. A way to improve the temporal resolution of the velocity time-series is to test whether the estimation of the relative seismic velocity changes dv/v obeys the ergodic hypothesis in which the joint use of colocated stations would lead to better resolved measurements. In this study, we present results from a dense seismic array that was deployed for 2 weeks at the remarkable Patache site in Chile. Thanks to high temporal averaging capabilities, we are able to resolve seismic velocity changes in the 3–6 Hz frequency band at a 10-min resolution around the occurrence of a moderate earthquake (PGV ∼1 cm s–1). We report a velocity drop of ∼0.4 per cent in the first 10 min after ground shaking. Half of this initial drop was recovered within the 2 following days. The shape of the recovery follows a log-linear shape over the whole observed recovery phase, analogous to slow dynamics experiments. When normalized by the total amount of processed data, we show that the ergodic hypothesis almost perfectly holds in our network: the dv/v signal-to-noise ratio (SNR) obtained when averaging a few observation with large stacking durations for the correlation functions is almost equal to the SNR when using a large number of observations with small stacking durations. To understand if the ergodicity is linked to a particular site property, we use the array capabilities to identify the surf at the shoreline as the source of the noise and to derive a 1-D shear velocity profile with the focal spot imaging technique and a transdimensional Bayesian inversion framework. The inversion shows that hard rocks lie close to the surface indicating that this material hosts the observed shallow velocity changes. We discuss our high-resolution measurements and attribute them to a stable noise source excited by the shore, the ergodicity property and an ideal subsurface structure. Finally, we discuss the effect of moderate earthquakes on subsurface damage and the potential relaxation processes in hard rocks.

Magnitude estimation and ground motion prediction to harness fiber optic distributed acoustic sensing for earthquake early warning

Earthquake early warning (EEW) systems provide seconds to tens of seconds of warning time before potentially-damaging ground motions are felt. For optimal warning times, seismic sensors should be installed as close as possible to expected earthquake sources. However, while the most hazardous earthquakes on Earth occur underwater, most seismological stations are located on-land; precious seconds may go by before these earthquakes are detected. In this work, we harness available optical fiber infrastructure for EEW using the novel approach of distributed acoustic sensing (DAS). DAS strain measurements of earthquakes from different regions are converted to ground motions using a real-time slant-stack approach, magnitudes are estimated using a theoretical earthquake source model, and ground shaking intensities are predicted via ground motion prediction equations. The results demonstrate the potential of DAS-based EEW and the significant time-gains that can be achieved compared to the use of standard sensors, in particular for offshore earthquakes.

The Influence of Input Motion Scaling Strategies on Nonlinear Ground Response Analyses of Soft Soil Deposits

A key issue for the estimation of ground shaking is the proper selection of input motions at the seismic bedrock. At the same time, the effect of the input motion scaling strategy on structural response is typically studied disregarding the presence of the soil deposit. In this work, different soft soil deposits are selected by varying the shear wave velocity profiles and the depth to the seismic bedrock, modelling the soil behaviour through a nonlinear constitutive model implemented into a fully coupled FE code. Seven input motions are retrieved for several selection strategies in conjunction with two seismic intensity levels. Hence, more than 300 one-dimensional ground response analyses are performed. The results of the analysed cases, which are presented in terms of spectral response at ground surface and amplification factors, indicate that: (i) the use of an advanced elasto-plastic soil constitutive model accounts for nonlinear ground response effects, including higher site amplification in the mid-period range and deamplification of the peak ground accelerations; (ii) the different scaling strategies lead to comparable mean values of the amplification factors, and (iii) the variability of the amplification factors is significantly reduced when the scaling strategy seeks the compatibility with the target spectrum over a specified period range. The research will aid the prediction of local seismic site response over large areas, particularly in the absence of the fundamental period of a structure and facilitate its use in general recommendation for quantifying and reducing uncertainty.

Probabilistic urban cascading multi-hazard risk assessment methodology for ground shaking and post-earthquake fires

A probabilistic methodology is presented for assessing cascading multi-hazard risk for ground shaking and post-earthquake fires at a regional scale. The proposed methodology focuses on direct economic losses to buildings caused by the combined effect of ground shaking and post-earthquake fires and evaluates the exceedance probability of the regional shaking–fire losses in a predefined future time period by comprehensively considering the effects of various uncertain factors on the losses via Monte Carlo simulations. Probabilistic seismic risk assessments are extended by integrating post-earthquake fire models with seismic activity models, ground motion prediction equations, and seismic fragility functions. The fire models include post-earthquake ignition models, a weather model, a physics-based urban fire spread model, and a fire brigade response model. This integrated modeling enables the incorporation of the following uncertain factors with causal relationships into the assessments: earthquake occurrence, ground motion intensity distribution, damage to buildings resulting from ground shaking, post-earthquake ignition occurrence and occupant firefighting, weather condition, fire brigade response time including time to detection, and damage to buildings resulting from post-earthquake urban fire spread. To demonstrate the methodology, a realistic case study is conducted for a historical urban area with closely spaced wooden buildings in Kyoto, Japan, focusing on possible large earthquakes along major active faults. Contrary to conventional single-hazard approaches, the results highlight the impact of multi-hazard consideration on risk assessments. This indicates that the methodology can be a useful tool for more appropriately understanding earthquake risk and promoting risk-informed decision-making in urban communities for risk reduction.

Earthquake Location Forecasting In Map Using XGBOOST Algorithm

Earthquake is one of the most threatening natural disasters which is caused due to the shaking of the earth’s surface. Common cause of earthquake is due to ground shaking, underground volcanic eruption. Here, XGBoost Algorithm is used to predict the location of the earthquake. In this paper, a earthquake location prediction method is proposed, which is based on the composition of a known system whose behaviour is administered according to the evaluation of more than two decades of seismic events and is designed as a time series using Machine learning. By analyzing the parameters such as Latitude, Magnitude, Depth, Longitude, Depth error, Gap, Time etc.

Empirically based approaches for the derivation of fragility curves of Italian RC building typologies

In this study, fragility curves for Italian RC building typologies are derived, by taking advantage of post-earthquake damage data gathered after the Irpinia (1980) and L'Aquila (2009) seismic events. The severity of the ground shaking is characterized by extrapolating peak ground acceleration values from updated INGV ShakeMaps and a global level of damage, consistently defined with the EMS-98 and accounting for both structural and non-structural damage observed on preselected building components, is associated with each inspected building. RC buildings are allocated to twenty-four building typologies, accounting for construction age, design level and number of storeys. Statistical processing of observational damage data showed the general tendency of seismic vulnerability to increase with the number of storeys and to reduce with design level and construction age. In some cases, the reliability of the obtained results was however affected by the limited amount of damage data and/or by scarcely populated building typologies. Two alternative empirically based approaches, relying on different data processing techniques and fitting strategies, are hence developed, overcoming issues in empirical fragility assessment driven by data paucity and allowing for a robust seismic fragility model.

ЗАТУХАНИЕ СЕЙСМИЧЕСКИХ ВОЛН В ЛИТОСФЕРЕ ПРИАМУРЬЯ

We present the results of determining the attenuation parameters of seismic waves (seismic quality factor at a frequency of 1 Hz Q0 and frequency parameter n) in the lithosphere of Priamurye. We estimated the attenuation parameters on a regional scale using code of Lg surface waves, as well as their key and strongest spatial variations. The Q0 parameter varies from 380 in southern Primorye to 600 in northwestern Priamurye. Based on the code of body S-waves from nearby earthquakes recorded at the stations of the local seismological network of the Bureyskaya Hydropower Plant, we obtained the average estimates of the quality factor and frequency parameter for a region with a radius of a few hundred kilometers around the hydropower plant. For a window width of 20 s, Q0 = 103 and n = 0.806. These values are typical for the regions with moderate seismicity and confirm the significant seismic potential of the territory. The use of the information about actual attenuation parameters of seismic waves makes it possible to more accurately and more understandably relate the parameters of the sources of hypothetical earthquakes and the expected intensity of ground shaking caused by them, and thereby eliminates one of the significant simplifications inherent in general seismic zoning maps.